ESTIMATION OF VARIOUS MECHANICAL CHARACTERISTICS OF HUMAN BONES USINGDUAL-ENERGY X-RAY ABSORPTIOMETRY - METHODOLOGY AND PRECISION

The mechanical competence of bone is determined by its macroscopic geo metric characteristics [size, shape, apparent density (BMAD), cortical thickness (CWT), cross-sectional area, trabecular architecture], intr insic material properties (stiffness, strength), and loading condition s (mode, direction, rate) at a given skeletal site, The main objective of this study was to introduce precise methods for further analysis o f dual energy X-ray absorptiometric (DXA) data and for estimating macr oscopic mechanical characteristics of bone at several skeletal sites r epresenting both the axial and appendicular skeleton, This study showe d that using computational BMAD, CWT and dimensional parameters, diffe rent site-specific mechanical charateristics (stiffness and strength i ndices) of a typical long bone (a bone consisting of both the cortical shaft and trabecular metaphyses and epiphyses at both ends) can be ap proximated with a low precision error (generally <2%). The efficacy of a study applying DXA may be further enhanced by applying relevant sit e-specific parameters (different parameters for bone ends and shafts) for evaluation, the parameters based on the anatomic ROIs, Evidently h igh-quality operator performance is a prerequisite for effective accom plishment of longitudinal studies, especially when small changes in bo ne characteristics are expected, It should be kept in mind that to som e extent the inherent two-dimensional nature of the DXA measurement co mpromizes the potential efficacy of the presented methods since some s imple assumptions had to be made regarding the geometry and structure of bone, Nevertheless, in this study the observed values were consiste nt with those found by other investigators, Further experimental studi es are needed for direct site-specific validation of the proposed anal ytic methods.